The purpose of this prospective study is to identify incidence and risk factors among several known groups within three regions of China so as to establish a base for observational evaluation of public health intervention and foundation for conducting focused clinical trials in China. China has the largest population of any nation in the world with over 1.3 billion persons (China Census Bureau, 2001). A tripling of prevalence from the current estimate of 0.05% to just 0.15% would represent an additional 1.3 million infected persons. A conceivable rise to 4% as was seen in parts of Thailand and now India would represent 52 million persons, more than are infected in then entire rest of the world. Hence, the urgency of HIV control in China cannot be overemphasized. There is much that is unknown about the scope of HIV risk in China. China's multicultural and multiethnic characteristics accompany wide geographic and socio-demographic variations. Knowledge of the "scene" in Beijing by no means informs what is happening in Yunnan, for example. While injecting drug users (IDUs) and commercial plasma donors (who have red cells reinfused without proper blood safety precautions) are two groups most heavily hit by human immunodeficiency virus (HIV) epidemic in China, inadequate surveillance has been in place to judge the extent of transmission both within these subgroups as well as to the general population. The resurgence of commercial sex work and dramatic rise in sexually transmitted infections (STI) bode ill for the HIV epidemic. Both had been nearly absent for over a generation such that Chinese authorities and health care workers have little experience in addressing CD either sex work or STI control within a public health context. A key goal of this study is to identify risk sexual behaviors that may result in HIV diffusion. If other Asian countries are good guides, female sex workers (FSWs) and men or women who migrate between high and low prevalence areas will be a bridge population from the two affected populations to the general public in China. Hence, sex work and migration patterns of infected persons will be primary research themes. Furthermore, we have identified groups in China (Xinjiang Autonomous Region) that have some of the highest rates of HHV-8 ever reported, up to 48.0%, and we intend to explore the relevant risk factors. Project One involves epidemiology as a backbone of the entire P01, studying the prevalence and incidence of HIV and STI among four key Chinese populations in the context of their drug and needle use, blood transfusion, sexual practices, migration patterns, and prevention-related behaviors and 2 attitudes. We have chosen populations that we believe to be of highest public health importance and that will provide insight into the broader Chinese prevention agenda. We will bridge these observational studies to health interventions, including prevention and therapeutic clinical trials, in years 2-3 of the CIPRA. Our FPD (FPD) and IDU studies will provide a subset of subjects (HIV positive) for the behavioral intervention study planned in Project 2. We will seek upgraded clinical care of all identified HIV infected persons, in collaboration with Project 4. Clinical specimens will be provided for key research initiatives described in Projects 3, 5, and 6. Planning for field trials of HIV vaccines will use the data from Project 1 for cohort development linked to Project 5.